One Call Now - One Call Now's message notification delivers automated phone calls, SMS text messages and emails within moments to any group.
PagerDuty - Cloud based monitoring service
Notifuse - A 1-to-many notification API that's simple to use
OpsGenie - Alerting and On-Call Management for Dev&Ops Teams
OnPage - OnPage critical alert and incident management system enables rapid resolution of critical IT, healthcare or IoT incidents through efficient communication.
Squadcast - Automate incident response, reduce downtime and enhance your tech teams’ delivery with a unified platform.